Conventionally, the position or intensity of the corrugations added in a direction orthogonal to the conveyance direction of a paper conveyance surface, i.e., a paper width direction, is changed to prevent the front end of a paper from hanging down.
However, a mechanical control needs to be carried out based on a sensor for detecting the width of a paper, a sensor for detecting the thickness of a paper and the detection results of the sensors. Consequently, more components are needed to carry out corrugating processing, which leads to an increase in cost.